Watch: Aw, Major Cuteness! First Ever Baby Sloth Is Born at the London Zoo

The London Zoo had no idea the two sloths even fancied each other. (London Zoo)

Birds do it, bees do it and, apparently, so do sloths.

Unbeknownst to their supervisors at the London Zoo, Marilyn and Leander, a pair of two-toed sloths at the Zoological Society of London’s menagerie, were doing what comes naturally on the sly. The result: a baby sloth, the first ever born at the London Zoo, arrived several weeks ago.

“Our two very sneaky sloths were getting amorous behind our backs!” said zookeeper Tegan McPhail in a report on the birth on the zoo’s website.

Zookeepers don’t yet know the sex of the still-to-be-named baby sloth, which has been clinging to its mother 24/7. Apparently, there are no external differences between sexes in sloths so zookeepers won’t know whether they have a baby boy or a baby girl sloth until vets get a chance to scan the little critter.

Here’s an adorable first look at the new arrival:

Want to know more about sloths? According to National Geographic, the animals, which are found in South America, are “the world’s slowest mammal, so sedentary that algae grows on its furry coat.” Also, and this falls under the don’t try this at home category, sloths mate and give birth while hanging in trees.